1. Field of the Invention
The present invention relates generally to an inter-computer communication system for performing communications between a plurality of computer systems connected to each other via communication lines. The present invention relates more particularly to an inter-computer communication system capable of automatically taking activation synchronism of respective computer systems.
2. Description of the Prior Art
A user system such as LAN (local Area Network) has hitherto been decentralized for making the communications attainable between remote places as well as for decentralizing a load on a host computer. This decentralized system has the following construction. A plurality of host computers are installed, and LAN is provided under each host computer. The respective host computers are connected using a WAN (Wide Area Network), such as a public network or a private line, and the communications between terminals belonging to respective LANs can communicate with each other through the respective host computers. Note that the host computer is also termed a "computer system" or simply a "system".
In such a decentralized system, when inter system communications is performed, both communication jobs, including a transmitting task of a transmitting-side system, and a receiving task of a receiving-side system, must be activated. A word "activation synchronism" connotes herein that both the communication job of the transmitting-side system and the communication job of the receiving-side system are activated. Under such circumstances, a question arises concerning how to take the activation synchronism between the respective systems.
In this respect, according to a conventional decentralized system, for instance, operators of respective systems contact each other on phones in order to establish communication paths by taking the activation synchronism between the respective systems, thus respectively activating the communication jobs beforehand. Otherwise, the operator of the transmitting-side system confirms that the receiving task of the receiving-side system is activated in advance, and thereafter activates the transmitting task of the transmitting system.
Note that if the receiving task of the receiving-side system is not activated while the transmitting task of the transmitting-side system is activated, the transmitting-side system must retry to establish the communication path through polling until the receiving task of the receiving-side system is activated.
In recent years, the decentralized system is going to spread not only between large-sized general-purpose computers but also between small-sized computers such as work stations and personal computers. It is therefore difficult take the activation synchronism between the transmitting-side system and the receiving-side system due to a difference in operation time zone which is attributed to a difference in type between computers. More specifically, in general, the large-sized general-purpose computer is operated so that the communication job stops once per week for maintenance and inspection. In contrast with this, in general, the small-sized computer is operated so that the communication job stops at night time every day. Accordingly, when the transmitting-side host computer is the large-sized general-purpose computer, and the receiving-side host computer is the small-sized computer, if the communication is performed at night, the receiving task of the receiving-side system can not be previously activated, and therefore the activation synchronism between the systems is hard to be taken.
Further, in such a case that the transmitting-side system executes a retrying process (that is, poling) for establishing the communication path until the receiving task of the receiving-side system is activated, if the WAN for connecting the respective systems is a public network, futile line using charges must be paid until the communication path is established.